This invention relates to a propulsion and stabilization system for an inductive repulsion type, magnetically levitated vehicle, and more specifically, to a magnetically levitated ("maglev") vehicle which is propelled and stabilized by a system which includes propulsion windings mounted above and parallel to vehicle-borne suspension magnets.
Maglev development began more than two decades ago in the United States, German, Japan, Canada and England. In the United States, renewed interest has been directed toward magnetic levitation transportation systems in view of such factors as energy conservation, high speed transportation at ground level, economic and environmental problems associated with conventional system, and composition from West Germany, France and Japan.
The use of electrodynamic suspension to provide levitation in maglev systems is well known in the prior art (see further, U.S. Pat. No. 3,470,828, issued Oct. 7, 1969, to Powell et al). A repulsive levitation (suspension) force is generated by the interaction between a magnetic field generated by superconducting magnets aboard the moving vehicle and eddy currents induced in the guideway by the time varying magnetic field of the passing magnet. The guideway can be made of a continuous sheet of a non-magnetic conductor, such as aluminum, or of discrete coils or loops of similar material. The vehicle may be advanced over the guideway by propeller, jet, rocket, or other suitable propulsion means.
The use of a linear synchronous motor (LSM) to propel a wheeled or levitated vehicle is also well known in the prior art (see further, Rhodes et al., "Magnetic Levitation for Rail Transport", 1981, pages 62-67), and several systems include a linear synchronous motor with an electrodynamic repulsion system to provide propulsion by magnetic means (see further, U.S. Pat. No. 3,815,511, issued Jun. 11, 1974, to Dukowicz et al).
The Japanese MLU-002 electrodynamic suspension system is one of the most highly developed system of this type in the world. Superconducting magnets on the vehicle react against conventional, normally conducting, coils in the guideway. In early tests, the superconducting magnets were placed in a horizontal position and reacted against horizontal coils on the bottom of the guideway. The superconducting magnets were later redesigned and located vertically, reacting with horizontal coils on the guideway for levitation and vertical coils located on the sidewalls of the guideway for guidance. The guidance coils are connected in a null-flux configuration to reduce the electromagnetic drag. Linear synchronous propulsion coils are also located on the sidewalls, but since they are symmetrically located with respect to the null-flux coils, they do not interact with them.
The basic components of the present magnetically levitated vehicle system have been identified and are well understood (see further, "Preliminary Design for a Maglev Development Facility", ANL/ESD-14). It is the object of this invention to device a configuration of those components which will achieve the highest synergy, that is, which will minimize the negative effects and maximize the positive effects of one component on the others.
The present invention departs from the prior art principally in its placement of coils for a linear synchronous motor (LSM). The LSM employs three phases of power with three distinct windings. In the prior art, the LSM coils have been placed in the roadbed below the superconducting magnets mounted on the vehicle, In some designs, these superconducting magnets are separated from the levitation magnets. The present invention places the coils of the LSM above and parallel to the superconducting magnets, and thereby achieves significant advantages. By placing the LSM coils above and parallel to the superconducting magnets mounted on the vehicle, the magnetic levitation and propulsion system of the present invention provides a constant propulsion force independent of momentary differences in suspension height and dampening of vertical motion of the vehicle. This is accomplished by dynamically varying the current in the LSM windings.
In addition, the configuration of the present invention enhances the stability of the vehicle, giving intrinsic, passive stabilization.
Further, by locating the linear synchronous motor away from the guideway, the present invention reduces the dissipation of power in the guideway by the LSM.
Also, the LSM generates a magnetic field which opposes the field generated by the onboard magnets, thereby reducing stray magnetic fields and reducing the need to shield passengers from exposure to the intense field of the vehicle magnet.
Finally, the present invention enhances the safety of the maglev system by having the vehicle magnets confined within the guideway.
Additional advantages, objects and novel features of the invention will become apparent to those skilled in the art upon examination of the following and by practice of the invention.